This invention relates to the electrodynamic suspension and guidance of moving vehicles in general and more particularly to an improved system for obtaining such suspension in a zero flux system.
It is well known that in the art that, in an electrodynamic guidance system for a moving vehicle, primary conductor loops or magnet loops can be mounted on the vehicle and used to produce in a secondary conductor loop or secondary conductor rail, preferably a plate of nonmagnetic material, eddy currents which generate magnetic repulsion forces and which act to maintain the vehicle in a suspended state. Furthermore lateral guidance or horizontal stabilization of the vehicle can be obtained by using additional secondary conductor means on the roadbed cooperating with the same or different primary conducting magnet loops in the vehicle. Preferably in such installations the primary conductor loops or magnet coils on the vehicle are superconducting coils. The secondary conductors are preferably made of an aluminum or an aluminum alloy and are sometimes referred to as lifting loops or stabilizing loops.
One of the earliest known magnetic suspension and guidance systems for a vehicle illustrating the system having magnets carrying large currents producing lifting forced by interacting with an electrically conductive portion of a track on a road bed or the like is shown in U.S. Pat. No. 1,020,943. As disclosed therein the lifting forces counteract the gravity of the vehicle and keeps the moving vehicle in a suspended state above the tracks. More recently a number of embodiments of an electrodynamic suspension guidance system using magnetic repulsive forces have been disclosed in U.S. Pat. No. 3,470,828. As disclosed in there a plurality of magnet systems are mounted to the vehicle, one behind the other in the travel direction. Each magnet system includes vehicle mounted superconducting magnet loops and track mounted normally conducting rail loops wound in the opposite sense. In the rail loops, which are disposed parallel next to each other in the travel direction and parallel to the vehicle loops, reaction forces are produced which keep the vehicle in a stable position in the horizontal plane. In this system, as soon as the vehicle and with it its vehicle loops, departs from a central position in the vertical direction the track loops will be permeated by a greater flux to generate a restoring force in the direction of what is referred to as the zero position. In this zero position virtually no currents are generated. Thus, this type of an electrodynamic suspension guidance system is referred to as a zero or null flux system.
In the arrangement described in that reference, additional stablizing loops for generating horizontal guidance forces may be disposed vertically above or below the superconducting loops. In addition it is also possible to mount the lifting loops needed for suspension either vertically next to the vehicle loops as shown on FIG. 11 or horizontally above and below the vehicle loops as shown on FIG. 13. Furthermore as illustrated by FIG. 19 of that reference they may be divided into several partial loops between which is located a vertically disposed stabilizing loop for the generation of a horizontal guidance force.
Another electrodynamic suspension guidance system having a zero flux system disposed on each side of the vehicle and an additional system in the center under the vehicle is disclosed int the publication "Cryogenics and Industrial Gases", Oct. 1969, pages 19 to 24. The laterally disposed zero flux systems are used for suspension and the system disposed under the vehicle for lateral guidance.
In each of these systems the vehicle mounted superconducting magnet coils which are disposed in pairs vertically above one another and energized in an opposite sense to each other are guided along side an electrically conductive, nonmagnetic, track mounted rail arranged horizontally and composed of a plurality of conductor loops disposed one behind the other in the travel direction in such a manner that the rail is located between two magnet coils disposed vertically above the other. The rail is thin in relation to the depth to which the magnetic field penetrates the rail material. As a result losses and the braking forces associated therewith are generated only when the rail is not located exactly in the middle between the coils of a respective pair of coils. In the first approximation, the braking force is proportional to the second power of the deflection from the zero position. The lifting force generated is, in the first approximation, directly proportional to the deflection. Because of this superposition of forces a stable suspension of the vehicle can be achieved.
However in the zero flux system the lifting loop or rail on the roadbed are not exactly in the center plane between the magnet coils which are above and below the rail because the weight of the vehicle and the mounting coils mounted thereon represent an additional force causing the upper magnet coils to be closer to the lifting loops than the lower magnet. That is to say, that there is a necessity that a force be generated to offset the force of gravity. As a result the spacing of the reaction rail relative to the magnet coils differ between the upper and lower coils. As a result the safety tolerance with respect to vertical motion of the vehicle is less in a downward direction than in the upward direction.
In view of this deficiency, it is an object of the present invention to provide an improved electrodynamic suspension system of this nature in which the vehicle is suspended using a zero flux system and in which the magnet coils are approximately symmetrical with respect to the secondary conductor loop or rail.